We start from the PSE formulation as reviewed by [1]}, using the Navier-Stokes (N-S) operators described in [2]}. In summary, solutions for the compressible linearised N-S equations are sought, which can be written in operator form as
\(\frac{\partial \mathbf {q}}{\partial t} + \mathbf {A} \mathbf {q} + \mathbf {B} \frac{\partial \mathbf {q}}{\partial x} + \mathbf {C} \frac{\partial \mathbf {q}}{\partial r} + \mathbf {D} \frac{\partial \mathbf {q}}{\partial \theta } + \frac{1}{Re} \mathbf {E}_{r,\theta } \mathbf {q} = 0.\) 
